core: adding migration related commands to the managed-allowed commands

This patch adds the InternalMigrateVm and MigrateVmToServer commands to
the allowed commands for managed VMs.

Change-Id: I319aebd42acc2397b51f9a340ab2e37747b22c18
Signed-off-by: Oved Ourfali <oourfali@redhat.com>